Flash Annealing Emissivity Mediator for Wafer Temperature Control
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Solution Overview
Problem
Existing heat treatment methods for semiconductor wafers face challenges in accurately measuring the surface temperature due to variations in emissivity caused by device patterns, leading to inconsistent activation of impurities during the annealing process.
Innovation Solution
A heat treatment apparatus and method that includes a chamber, a holder, an irradiation part, a quartz window, a photodetector element, a filter, a back-surface temperature measuring part, and an emissivity calculating part to measure and calculate the temperature of the front surface of the substrate independently of device patterns by eliminating specific wavelength ranges and using selective wavelength filtering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If flash lamp annealing is used to rapidly heat the substrate surface, then impurity activation is achieved without deep diffusion, but accurate temperature measurement becomes difficult due to emissivity variations from device patterns
Solution Approach 1:
The patent introduces a mediator substance (such as molybdenum silicide, tungsten silicide, or tungsten) with known and stable emissivity that is formed on the substrate surface before flash lamp annealing. This mediator serves as an intermediary layer that allows accurate temperature measurement by providing a consistent emissivity value, thereby resolving the measurement difficulty caused by variable emissivity from device patterns. The mediator layer is subsequently removed after the annealing process completes.
Solution Approach 2:
The patent changes the emissivity parameter of the substrate surface by forming a mediator layer with known and stable emissivity characteristics. This parameter change enables accurate temperature measurement during flash lamp annealing, as the mediator layer's consistent emissivity allows the temperature measurement apparatus to accurately determine surface temperature without being affected by the underlying device pattern variations.
2Reliability
If conventional annealing is used to activate impurities, then sufficient activation is achieved, but impurity diffusion depth becomes too great
Solution Approach 1:
The patent employs periodic or pulsed heating action through flash lamp annealing, which delivers intense heat in extremely short durations (microseconds to milliseconds). This periodic thermal action activates impurities effectively while limiting the time available for diffusion, thereby achieving reliable impurity activation with minimal diffusion depth. The process uses repeated or continuous pulsed lighting to maintain temperature control.
Solution Approach 2:
The patent applies the principle of rushing through the annealing process by using flash lamp heating that delivers the required thermal energy in extremely short time periods. The intense but brief heating pulse activates impurities before significant diffusion can occur, effectively 'skipping' over the diffusion phase that plagues conventional slow annealing processes.
3Speed
If light energy is absorbed by the substrate surface, then rapid temperature rise is achieved, but temperature measurement becomes inaccurate due to unknown emissivity
Solution Approach 1:
The patent introduces a mediator layer with known and stable emissivity that is formed on the substrate surface before flash lamp annealing. This mediator serves as an intermediary that enables accurate temperature measurement by providing a consistent emissivity value, thereby resolving the measurement difficulty caused by variable emissivity from device patterns. The mediator layer is subsequently removed after the annealing process completes.
Solution Approach 2:
The patent changes the emissivity parameter of the substrate surface by forming a mediator layer with known and stable emissivity characteristics. This parameter change enables accurate temperature measurement during flash lamp annealing, as the mediator layer's consistent emissivity allows the temperature measurement apparatus to accurately determine surface temperature without being affected by the underlying device pattern variations.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate temperature measurement and control of the front surface of the substrate, ensuring consistent activation of impurities without deep diffusion, thereby improving the formation of semiconductor devices.
Implementation Method 1
a photodetector element provided on the front surface side of the substrate, for receiving radiated light from the front surface
Implementation Method 2
a filter for selectively allowing light having a selective wavelength range included in radiated light directed from the front surface of the substrate toward the photodetector element to pass therethrough
Implementation Method 3
a quartz window provided in the chamber, for eliminating light having a predetermined wavelength range from light emitted from the irradiation part
Implementation Method 4
an irradiation part for irradiating the front surface of the substrate held by the holder with light
Implementation Method 5
for heating a thin plate-like precision electronic substrate by irradiating the substrate with light
Data Source
AI summary
After flash irradiation on a semiconductor wafer is started and then the temperatures of front and back surfaces of the semiconductor wafer become equal to each other, the temperature of the back surface of the semiconductor wafer, which has a known emissivity, is measured with a radiation thermometer. The emissivity of the front surface of the semiconductor wafer is calculated based on the intensity of radiated light from a black body having an equal temperature to the temperature of the back surface thereof, and the intensity of radiated light actually radiated from the front surface of the semiconductor wafer. Then, the temperature of the front surface of the semiconductor wafer heated by the flash irradiation is calculated based on the calculated emissivity and the intensity of the radiated light from the front surface of the semiconductor wafer that has been measured after the flash irradiation is started.